A lot of really good older games have been ported to mobile and work fantastically. Knights of the Old Republic, Neverwinter Nights, and Baldur’s Gate just to name a few. Hell, you can play Baldur’s Gate multiplayer, cross-platform with PC players even! There’s also fo2.exe on the Play Store, which lets you play Fallout 1 & 2 on mobile provided you have access to the files from the PC versions. Oh, and Doom ports galore, of course.
As far as mobile-only or mobile-specific games, my favorite is probably Caves, a surprisingly well done and completely free roguelike.
Also an honorable mention goes to Organ Trail, a zombie-themed take on Oregon Trail that is, frankly, just a flatly better version of the game in almost all regards. The only reason it’s not my favorite is because the controls on mobile feel awkward compared to the PC version. Still fun though.
Slay the Spire is excellent on mobile, it’s a roguelike deck builder.
Marvel Snap is a really fun lightweight TCG kinda thingy. I never liked Hearth stone or Runeterra, however I thoroughly enjoy Snap
Cytus II, it’s a great rhythm game with a cool storyline
Hate to break it to you, but Rayark replaced it’s art department with AI, so I wouldn’t support them.
Arcaea is good though from what I know, and if not that, there’s also opsu! and the osu! lazer port for android.
N.O.V.A 3 (Near Orbit Vanguard Alliance). It is a mobile FPS with a pretty good campaign. Bonus points if you can find it without ads.
One More Line is pretty great.
I used to play a ton of rocket league on pc. I was upset at one point by some of their decisions. However i have really been enjoying their free mobile game rocket league sideswipe. It’s different than other games so that ticks the box and there is a lot of room to grow skill wise.
RCT classic is pretty good. Not as good as OpenRCT but still quite good.
Slay The Spire is also very good, though the mobile version is a bit bigger than the PC game
Definitely the mobile version of Stardew Valley
May be the commercial one but actually Candy crush is a nice one
I work at a gaming company - Candy crush is known for employing the same tactics that keep people sitting at slot machines for 8 hours a day, and every damn PM wants to copy those patterns.